Control means for heat applying apparatus



y 16, 1940- c. w. WALTER 7 2,208,552

CONTROL MEANS FOR HEAT APPLYING APPARATUS Filed June 24, 1935 5 Sheets-Shqet 1 Invenior: UarZ W Wa /Kiev; I) 14; WM Edi/ 3398- c. w. WALTER 2,208,552

CONTROL MEANS FOR HEAT APPLYING APPARATUS Filed June 24; 1935 3 Sheets-Sheet 2 July 16, 1940.

July 16, 1940. f LTE 2,208,552

CONTROL MEANS FOR HEAT APPLYING APPARATUS Filed June 24, 1935 3 Sheets-Sheet 5 RED GREEN WHITE 2.3 mg $12 $12 /L /00 so /9/- 96 as E L Q m c 1 2 j 5: IW/veW/Zo W ZIP UaWZ WWaZi/en' IIIIIIII [1:1] 3 a I I, MFW

(y z 1 l7 viii/gs Patented July 16, 1940 UNITED STATES PATENT OFFICE CONTROL MEANS FOR HEAT APPLYING APPARATUS 42 Claims.

My present invention relates broadly to controlling the application of heat in the treatment of various media, whether solid or fluid media. More particularly it aims to provide largely automatic, substantially fool-proof, and otherwise improved methods of and apparatus for sterilizing or other heat treatment at prescribed temperatures and for predetermined time periods, as and for those purposes, among others, as hereinafter set forth.

In the drawings illustrating by way of example certain embodiments of means of my invention, and whereby the method thereof may be practised,

Fig. 1 is a view mainly in section illustrating the invention in association with an autoclave or sterilizer;

Fig. 2 is a front elevation of the charging end of the apparatus oi Fig. 1, upon a larger scale;

Fig. 3 is a section on the line 33 in Fig. 2;

Fig. 4 is an enlarged view of a switch mechanism operated by the charging door;

Fig. 5 is a wiring diagram;

Figs. 6 and 7 are front and rear views of an instrument housing or panel;'

Figs. 8 and 9 are respectively side and end elevations of another form of apparatus embodying the invention; and

Fig. 10 is an enlarged sectional view of one form of switch and locking mechanism adapted for use in connection with the apparatus of Figs. 8 and 9.

The apparatus selected for the purpose of iilustrating embodiments of my invention may be considered as typical of sterilizers, autoclaves and the like such as commonly employed in hospitals, clinics, laboratories and such plates for sterilizing dressings and other hospital materials, surgical instruments and utensils, solutions and other items. In Figs. 1 to 3 I have shown a sterilizer or autoclave of the pressure steam type, and in Figs. 8 and 9 a so-called instrument sterilizer which makes use of a liquid bath or boiling "method. It will be understood that the invention both as to means and method is also applicable to various other devices of a non-pressure or atmospheric steam type (such as the Arnold sterilizer), as well as to dry or hot air types of sterillzers, and to otherheat-applying apparatus.

Referring first more particularly to Figs. 1 to '7, the sterilizing chamber, receptacle or receiver indicated at It has a surrounding steam jacket at H. The chamber is adapted to be closed by the usual steam-tight charging door l2 having hinged support at l3 and arranged to be held in closed position by the series of radius bolts H manually operated by the handles I5.

Steam from any suitable source, local or otherwise, is admitted to the jacket through the steam inlets l6, It. From the jacket steam is conducted to the receptacle or chamber of the sterilizer via the pipe ll. As herein illustrated, in accordance with one feature of the invention, I have provided for admission of steam to the chamber at a plurality of points distributed over the interior of the chamber, including particularly the upper portion thereof, as indicated by the several upper inlets I8, l8, it, each equipped with deflectors I9. These inlets are supplemental to'an inlet II at the rear portion of the chamber, corresponding to the usual single inlet at such location. In this manner the steam is more rapidly admitted, is distributed uniformly and is immediately effective over substantially the entire upper portion of the chamber, whence it drives the air downwardly for discharge. The steam is thus compelled to pass downwardly through and between the various items of the load and to force out the air contents, uniformly, throughout the entire chamber, avoiding cool spots and delayed action, particularly at the front or intermediate localities. The usual chamber exhaust, for releasing the steam after a sterilizing operation, is indicated at and the exhaust line at 2 l. Valves and operating means 22, 23 are located in the steam inlet and exhaust lines of the chamber, respectively. They are illustrated as of the manual type but may be electrically operated automatically if desired, as noted later herein. Pressure gauges as indicated at 24 may be provided for the steam jacket and for the chamber, but, as will be apparent, such gauges are incidental only, and need not be relied on in the practice of my invention. The usual safety valve 25 and an air ejector valve 26 may also be provided.

Sterilizers of the general class illustrated comprise mainly two types, as regards their principle of operation, namely, the so-called vacuum type, and the forced evacuation type, or, as here, the sterilizer may be equipped to operate in the man ner of either type. In the former a partial vacuum is created in the chamber before steam is admitted to it, by means of an ejector device, such as indicated at 26, controlled by an operating valve, whereby steam from the jacket pumps out or ejects a portion of the air from the sterilizer chamber. About a 10 to 12" vacuum (in terms of a 30-inch mercury column) is the maximum ordinarily obtainable. That is, about twothirds of the air remains in the chamber, a factor productive of considerable uncertainty in the sterilizing operation as ordinarily performed.

In the forced evacuation type, the chamber steam itself is used to force out the air, through a discharge outlet at the bottom of the chamber. Substantially complete evacuation of the air can thus be accomplished, and in about the same time as required for removing but one-third the air by the vacuum method. My invention is equally applicable in connection with sterilizers arranged for either or both of said methods of operation.

Referring again to Fig. l, the air and condensate discharge passage, as above mentioned, comprises an outlet 30 from the lower part of the chamber and a lead-ofi pipe 3| communicating with a waste receiver or waste line, not necessary to show, and which desirably is equipped in the known manner to prevent back flow of foul water or material from the drain lines. The discharge passage preferablyhas in it a removable screen 32 for collecting lint, lime, or other sediment and preventing clogging of the passage.

Control of such discharge passage in the illustrated type of air-evacuating sterilizer may be by means of a manual vent valve worked by the operator. After steam from the jacket has been admitted to the chamber, opening of such vent valve allows the air to be forced out. A following flow of steam will inform the operator that the chamber has been substantially exhausted of air, whereupon he closes the vent valve, to allow the steam pressure to build up in the receptacle.

Instead of such manual control of the air and condensate discharge passage, automatic thermostatic control 'may be afforded, as in the illustrated instance. Accordingly a thermally operated valve 33 is set in the discharge passage, preferably at a location, such as at the end of the pipe 3|, close enough to the outlet itself asto be subject to substantially the same temperature condition as in the outlet. It will be apparent that the discharge passage 30, 3| is in effect. a portion, and herein the lowermost portion, of the sterilizer chamber or receptacle, being in direct communication with it. And since it is at Y or adjacent the bottom of the sterilizer the temperature within it will be indicative of that of the sterilizer fluid temperature at the coolest portion of. the receptacle, as represented by the temperature of the discharge fluid.

With such thermal control of the discharge passage the operator's duties remain the same, except that he is relieved from manipulating the discharge valve, during proper functioning of the thermal valve. Assuming that steam under adequate pressure, from the available source, has been admitted to the jacket, the chamber or receptacle is loaded through the charging door and the latter closed and bolted by turning up the operating handles IE to project the radius bolts l4. Steam is then admitted to the chamber via the pipe I! and the plurality of distributed inlets I8. The entering steam seeks the upper portion of the chamber where it gradually builds up some pressure. The air naturally gravitates to the bottom of the chamber, assisted by said pressure, where it is discharged, with any condensate from the steam, through the cool and accordingly open thermal valve 33. The free air in the chamber is thus gradually evacuated, together with the air from the load to be sterilized. The time required varies with the character of the load and the size and number of the parcels, bundles, containersJ drums or other articles comprising the load. The manner in which the bundles and articles are positioned in the receptacle or chamber also has a considerable effect as to the time required to free the chamber of the air from within and between the pieces. When the air and condensate have been discharged to such extent that a relatively free discharge of steam occurs, the thermal valve 33 closes partly or fully, and the pressure in the chamber accordingly builds up to that available.

From this stage, and to the end of the sterilizing cycle, in any previous apparatus of which I am aware, the production of certainly sterile goods and materials is largely dependent on the attentiveness and care exercised by the nurse or operator.

The prevailing practice has been for the operator to observe the chamber pressure gauge and to consider the pressure reading there as correctly indicative of the temperature in the receptacle or chamber. When a pressure indication equivalent to the desired temperature (15 pounds for 250 F.) is reached-but not before-the operator must start to time the assumed actual sterilizing period, by setting the time to running on a clock or other timing device. At the end of the prescribed interval, which may be 15, or 20, or 30 minutes or more, if the operator has not seen the pressure gauge drop below the 15 pound indication, it is presumed that sterilization has taken place. The steam from the jacket is shut off, the steam exhaust valve 23 is opened and after a short period for allowing the steam to escape and the material to dry, the load is removed, in assumed sterile condition.

The operation as described necessarily involves a large human factor. The attendant must not set the time too early, nor skimp on the time prescribed. Even with ordinary attentiveness the operator may fail to note that the pressure has dropped, due perhaps to failure of the steam supply, or to faulty operation of the discharge valve. Low pressure, and the accompanying low temperature, even for a few minutes, perhaps while the operator has left the room, may destroy the effectiveness of the whole cycle.

But in addition to the opportunities for error by reason of the human equation, the operation described has the serious fault that chamber pressure readings are not reliable as correctly indicative either of chamber temperatures or of sterilizing conditions within the load. While it is true that live steam at a given pressure has a characteristic temperature, for example, 250 F. at 15 pounds pressure, it cannot safely be assumed that a pressure reading at the gauge is due entirely to the action of steam in the chamber at the equivalent temperature. Even with a thermally controlled discharge valve, the chamber may contain a mixture of air and steam or condensate, particularly in the initial stages, or if the load has been improperly positioned, and a pressure reading under such conditions may not involve a temperature equal to that of pure steam at the indicated pressure. Or the air and condensate discharge passage 30 or its thermal valve 33 may become clogged, allowing air and condensate to be trapped in the chamber, and causing the building up of a pressure indicative of a much higher temperature than is actually present. The pressure gauge reading gives the operator no indication of such condition. Further, even with all parts functioning properly, and with the chamber pressure reading accordingly showing substantially correctly the chamber temperature, there is no assurance that the time interval allowed is adequate for a thorough penetration of the steam and heat into the largest or most heat-resistant bundles or articles comprised in the load. And a mere prolonging of the period will not remedy the situation unless the actual temperature is adequate, as contrasted with the pressure indication.

This latter fact has been recognized, and it is, now common practice to place checking devices or so-called controls in the bundles or materials to be sterilized, such as the devices known commercially asiDyack controls, or those shown in Patents No. 1,788,104 or No. 1,894,015. when such devices function accurately it is reasonably safe to assume that the material in their immediate vicinity has been subject to sterilizing conditions. The intention is that when the load is removed, such checking devices shall be examined, and if they do not show a change characteristic of a sterilizing condition, the material of the load is to be returned to the sterilizer for further treatment. But such is not always the practice, and for one reason or another said "controls or checking devices even when indicating accurately, may be wrongly read or simply disregarded.

Recently it has also to some extent been recognized that the use of a temperature indication in connection with the sterilizer receptacle or chamber, or some portion or communicating extension of the chamber, might give more certain results than can be had by relying on a chamber pressure reading. Applicant is aware that recently it has been proposed to provide a thermometer, or temperature recorder, visible to the op-' 'erator, and operatively located to indicate or record the temperature at some location in' or adjacent the load-containing receptacle or chamber of a sterilizer. That is a step in the right direction. Properly functioning and used, it may avoid some of the inaccuracies of the pressure-reading method of operation. But the mere provision of such visual indication of the temperature condition does not obviate the objectionable human factors. There is nothing to prevent the nurse or operator from setting the time, for the sterilizing period, too soon, before the'desired 250 F. or other prescribed temperature is indicated, or from skimplng the prescribed period and removing the load too early. carelessly, or otherwise, the operator may disregard the temperature indication or record and proceed entirely independently of it. And there is no assurance that the operator, however conscientious, will select the proper sterilizing period for a load of a given character and size. Ithas also presently been proposed to provid a time-measuring means inautomatic association with such temperature indicating or recordingdevice. Under such proposal a liquid thermometer is operatively located in the path of the discharge fluid in the discharge passage. At the desired temperature the-thermometer is intended to close a circuit which is effective to start a clock to measure off the sterilizing period, at the end of which period the steam is shut off, either automatically or by the operator, and the sterilizing is assumed to have. been effected. Under such arrangement the purpose is that the clock does not start to measure the time until a sterilizing temperature is reached; and that if such temperature is not held the action of the clock is stopped, but starts again where it left of! if the sterilizing tempera;- ture returns. i

It will be noted that-in accordance with such operation the'ciock may measure ofl a total period equal to the desired sterilizing interval, but a duration, no appreciable harm may have been done. But if more protracted the sterilizer receptacle or chamber may have cooled to such extent that a substantial period may be required, after the temperature has been restored, to bring the temperature'and sterilizing conditions in or adjacent the load back to what they were when the temperature failure occurred. All this may be unknown to the operator or may be disregarded if observed. 7

But what is still more important, with respect to any such proposed arrangement,-even though automatic and temperature-responsive to the extent referred to, is that the entire apparatus remains subject to the will of the opertaor, who may inaccurately read the indicator or recorder, or may negligently or wilfully skimp the sterilizing period, may shorten the period set on the clock, or simply disregard the latter, turn 01! and exhaust the steam and remove the load while still non-sterile in whole or in part.

In contrast with any of the systems and operating methods previously referred to, I propose, in accordance with my present invention, substantially to eliminate thehuman factor, partly by utilizing direct and accurate temperature (as contrasted with pressure) indication at characteristic and critical locations with respect to the sterilizer receptacle or chamber and the load contained, and further by making it absolutelycompulsory, irrespectiveof the will of the operator, that a load once placed in position in the receptacleand chamber must remain there until it shall have been subject in its entirety to a sterilizing condition, at a selected minimum temperature, and throughout a predetermined and consecutive time period. Such consecutive period, following my invention, is to be contrasted with an equal total but interrupted or non-consecutive period of supposed sterilizing conditions. Iln other words, my invention insures that a predetermined heat application, selected as appropriate to the particularload, and as measured by consecutive time units of heat above a specified minimum temperature, is certainly'and positively attained, Hence inattentiveness, carelessness or even wilful neglect on the operators part can have no harmful consequences.

Returning now to Figs. 1 to 4, 6'and 7, I will first refer to the several instrumentalities without detailing their operating circuits, the latter tobe described in connection with the wiring diagram of Fig. 5.

At a convenient point, as upon the door casing, '1 mount a multiple-contact electric switch '40 arranged to be operated in the course of closing and bolting the door or other closure. As

illustrated, the switch has an operating finger 40' projecting through the door casing and into the path of one of the radius bolts i4. As the latter is moved into bolting position the switch finger 40' is lifted and throws the switch. The

, latter includes a double-contact arm 42 engageable with either of a pair of contacts 43 and 44, and also includes another pair of contacts 45, 46; see Fig. 4. In the completely closed and bolted position of the door contacts 42, 43 and 45, 4.8 are closed, while with the door unbolted or open contacts 42, 44 close and the others open, under spring action.

The closing and bolting of the door thus serves to condition certain of the circuits, including that for positively locking the door. Moreover, the switch mechanism is so constructed and arranged with respectto the closure or door that the contacts are necessarily operated in a definite ch'ronological order. In this instance the contacts 45 and 46 close first, at an appreciable interval prior to closing of contacts 42 and 43, as the door is bolted. In the subsequent unbolting and opening of the door, contacts 42 and 43 open prior to the opening of contacts 45 and 46 and the closing of contacts 42 and 44. This is herein accomplished, as best seen in Fig. 4, by providing the switch-operating plunger 40', operated by one of the radial bolts I4, with a reduced portion which passes through the contact arm 43 and engages contact arm 45 before the larger portion of the plunger engages the contact arm 42, as the door is closed and bolted, and reversely when it is unbolted for opening. I

Automatic closure-locking means, as distinguished from the manually operated radius bolts, is herein so arranged that at the institution of a cycle the closure or door is locked and normally must so remain until the desired predetermined condition has been reached. Provision may be made for emergency release of the lock by some authorized person. In the illustrative embodimentthe door-docking means comprises a magnetic device shown as a double-acting solenoid 50. The plunger 5| controlled by the solenoid is movable in the door casing, either into locking engagement with the door, as shown in Fig. 3, or into retracted unlocking position. The two coil elements 50 and 5|) of the solenoid have a common terminal 52. The terminal for the locking coil is indicated at 53 (Fig. 5) and that for the unlocking coil at 54. This door-lock also embodies a double-pole toggle switch having the blades 55 and 56 respectively associated with contacts 51 and 58, the two blades being thrown from one position to the other by the solenoid as it locks or unlocks the door.

Desirably the control equipment is such that the sterilizer may be set for two or more different sterilizing periods, that period being selected which is appropriate for the particular load. For example, for certain articles and smaller bundles a twenty-minute period of consecutively maintained sterilizing heat at the coolest part of the sterilizer may. be adequate, while for other loads such as large bundles and materials in drums, a longer period of sustained temperature may be requisite to a thorough-sterilization of the entire mass. As herein illustrated two such selective sterilization periods are provided for, which will hereinafter be referred to as the A cycle and the B cycle of operation.

For selecting as between these two cycles or periods of operation I provide a four-pole doublethrow switch 60 including three pairs of contacts .BI and 62, 63 and 64, and G5 and 66, together with a fourth pair of contacts 61 and 68 having a common contact 69 engageable with either of them. This switch 60 may be located at any convenient point, on the sterilizer or elsewhere, as on an instrument housing or panel as shown in Figs. 6 and '7. The switch is of a type operated by a removable key adapted to be inserted in a key hole as at 60 the intention being that only the hospital superintendent or other responsible person in charge shall have access to the key, so that when the sterilizer is set for a selected type of operation no unauthorized person tampering with it can change the operating period. As illustrated in the diagram, Fig. 5, the contacts 62, 63, 65 and 69 are the movable ele-. ments. They are to be thrown to the right in said figure, as indicated by the arrow and the letter A, for the "A sterilization cycle, and to the left, as indicated by the arrow and the letter B, for the B cycle. Thus for the A" cycle, contacts 6| and 62, and 61 and 69 are closed, the others being open, while for the B cycle the reverse is true.

My control apparatus includes as an important feature circuit-controlling means which is automatically responsive at a set critical temperature at the selected locality, to institute, interrupt or repeat an automatic timing of the predetermined consecutive sterilizing period and, if desired, to cause a visual or other indication that said active period of sterilization has or has not started, or has been interrupted or is completed. For this purpose I provide one or more adjustable thermally responsive switches of an extremely sensitive and accurate character, for example, such as that of the patent to Wilfred J. Turenne, No. 1,535,751, dated April 28, 1925. One such thermo-switch may be located at what is usually the coolest part of the sterilizer, generally adjacent the bottom of the latter. This suitably may be within the chamber near the discharge outlet, or upon the inner face of the door, which location actual tests have shown generally to be in a relatively cool region or area in a sterilizer, such as shown by way of example in Figs. 1 to 3, which does not have a steam-jacketed door, or as illustrated in Fig. 1, I may set such thermoswitch 10 in the path of the-discharge fluid, air or condensate in the discharge passage 30, 3I and in advance of the thermo-valve 33 which controls the discharge. I

This thermo-switch '10 so located at a cool region of the sterilizer receptacle or chamber may be used as the single control, for example, in connection with articles of small size or which are relatively easy to sterilize, under what I herein refer to as the cycle 13 operation. For such operation it is entirely safe to assume that if a cool portion of the chamber, such as the discharge passage, is held at the critical temperature for a certain continuous period, say twenty minutes, it is morally certain that the entire load has been exposed to sterilizing temperature for an adequate time, including an ample safety factor. For example, the measured period may be set at three times the known germicidally efiective period for the particular goods or articles in question.

For the operating cycle A, I provide one or more similar thermo-switches 15 and 15, Figs. 1 and 3, either in addition to or alternatively for the switch 10, wherever located. Where the latter is used, the additional switch or switches are operatively disposed in parallel relation with it, so that both or all of the thermo-switches must operate before the time measurement starts.

The thermo-switch 15, having internal contacts 16, 11 (Fig. 5), is readily removably set into a heat insulated housing 18, in the instance shown in Fig. 3, which may be located at any convenient point within the chamber, as for example on the inner face of the door I2, as shown. The material and construction of the switch housing 18 is such as to correspond in heat resistance to that of the largest or most difil: cult load or bundle to be treated'in the sterilizer. This is readily determined experimentally and if desired the housing may be provided with vari-- ablevents or other adjusting means for'regulating it to any given condition. Said thermo-, switch 15 is connectedas by a flexible cord 15'' and plug receivable in aplural-outlet socket: 19

conveniently located within the chamber and in wired communication with leads I8, 11' of Fig. 5. Such predeterminedly insulated switch may, as stated, be positioned at any convenient point, and hence is independent of the particular construction of any given sterilizer. In sterilizers such as illustrated in Figs. 1 to 3, wherein the steam is admitted from above or at the far end and the door is not steam-jacketed or otherwise specially insulated, a cool zone or region, as previously indicated, is directly at the inner face of the door itself, more particularly a portion thereof spaced from the top of the sterilizer, as demonstrable by actual tests. This fact presumably is due to radiative or convective efiects at the door, so that at least a portion of the inner face of the latter maintains a relatively low temperature as compared with other locations in the sterilizer, for a time period substantially greater than that necessary for the penetration of heat at sterilizing temperature entirely through even the most resistant loads. Accordingly, in such instances, special insulation for the thermo-switch may be dispensed with and the desired result of assured sterilizing temperature throughout any load may be obtained by locating a thermo-switch I5 directly at such portion of the inner face of the door.

The thermo-switch I5 Fig. 1, may be used in addition to or alternatively for the insulated thermo-switch I5. It is intended to be embedded at that position in a relatively large bundle which is most resistant to the penetration of the heat, generally at the lower central part of the bundle, as illustrated in Fig. l. A flexible cord and plug connection I9 for the switch adapts it for insertion in said plural socket I9 When a number of sterilizing operations are to be performed in close succession, it is contemplated that the thermo-switches will beremoved be-. tween operations and replaced by duplicates which have in the meantime been cooling. If desired, the arrangement may be such that an operating cycle cannot be started unless the thermo-switch or the plurality of them then in place are in their proper initial or cool state wherein their contacts are closed, in the case of devices such as those of the patent referred to. This may be efl'ected by the use of a jack switch and associated additional contact on therotary switch to be described, the jack switch arranged to close on removal of the associated thermoswitch but remaining openand so preventing a normal cycle of the apparatus unless the thermoswitch is removed and replaced.

The thermo-switch I or the plurality of them are herein used to set up or selectively condition what will hereinafter be termed the thermo-controlled cold and hot circuits. These include a primary or relayoperating circuit, and secondary or operating circuits which are selectively controlled by the relay. The relay circuit, in which the thermo-switches are disposed, in parallel when a plurality are used, includes a relay 80 of a double-pole, double-throw type having terminals at 80, 82. This relay when energized is effective to move the connected contact arms 83 and 83* into closed engagement with contacts 84 and 80* thereby establishing certain "cold circuits, as for locking the door, and giving the appropriate signal, in a manner to be described. When deenergized the relay 80 allows the spring-loaded arms 83 and 80* respectively to engage a second pairof contacts 85 and 00 ton condition the hot or time-measuring cir- 0 ts.

Signals indicative of the operative status of the apparatus desirably are provided, either of an audible or visual type. I have illustrated for the purpose a plurality of pilot lamps including a red pilot 90, a green pilot 93, and a white pilot 06; see Figs. 6 and 7. The red pilot, when showing, indicates that a cycle is in progress but that the critical temperature either has not as yet been attained or has failed and not yet returned, or that the cycle has been completed and the steam turned 01?. The green pilot affords indication that the temperature at the characteristic locality where the measurement is taken has reached the sterilizing point of 250 F., or whatever temperature is desired, and that the period of time-measured heat-treatment or active sterilization is in progress. The white pilot signifies that a full consecutive heating or sterilizing period has been completed and that the door is unlocked, so that the steam may be turned oil and the sterilized contents of the chamber cooled and removed.

The steam inlet and exhaust valves 22, 23, as before noted. may be arranged for automatic operation, both initially and at completion of the sterilizing period. That may readily be accomplished by substituting electrically controlled valves arranged either in series or in shunt circuits with those for the appropriate pilots. For example, when the white pilot is lighted, the steam inlet would close and the steam exhaust valve open. But since in any event an attendant must manipulate the door and the load, it is entirely convenient for him also to operate the steam valves, as found in actual practice.

It is of far greater importance, in accordance with my invention, to insure that a full and continuous sterilizing period at the prescribed effective temperature has elapsed before it is possible to remove the contents. That ls herein accomplished, whether the steam valves are operated manually or automatically. For example, should a nurse or attendant under pressure of work attempt to shorten the sterilizing period by manuallyturning off the steam and opening the exhaust, nothing is gained, since the door still re:

mains locked. To the contrary, .a person so tampering with the apparatus will merely lose time, since the shutting oil of the steam and the attendant drop in chamber temperature will cause the entire cycle to be repeated in full.

For performing the actual timing operation I provide a relay I00, Figs. 5 and 7, arranged in circuit with a master clock, or other device, for producing electrical and/or mechanical impulses at timed intervals, of say one minute, such as a synchronous motor of the well known type operating directly from a timed alternating circuit. At such intervals the relay I00 momentarily moves the spring-loaded contact arm IOI so as to close a measuring circuit at a contact I02.

Aside from the thermo-switch relay circuit and the door-controlled circuits, the various other circuits, including those calling for a repeat cycle in the event of heat failure, are controlled by means of a rotary switch of a plural-plate type. For convenience in illustration and description the three plates or arcuate segmental strips H0, I20 and I30 of-this rotary switch, and the associated rotary contact arms III, I2I and lil respectively, are shown separately in the wiring diagram of Fig. 5, but it will be understood that the three arms are mounted upon a common arbor and all move simultaneously, step by step. This rotary switch, which may be a unitary device mounted on the housing or panel with the other instruments as shown in Figs. 6 and '7, includes a solenoid H2 having terminals H3, H4. This solenoid of the rotary switch is arranged to be energized periodically, as determined at times by the master clock and at other times by an interrupter device Ill to be referred to.

When the solenoid is thus momentarily energized, an associated armature element H2 acts to draw the pawl H6 across one tooth of the ratchet M6 on the contact arm arbor. On subsequent deenergizing of the solenoid the pawl is thrown back by its spring I I, causing it to step the ratchet and the several rotary contact arms through one unit or segment of the contact plates. When operating through the interrupter device, the solenoid ll2 itself acts on the interrupter M1, by means of a dog |l5 on the pawl, thereby breaking the solenoid circuit between a pair of contacts H8 and 'I iii.

The rotary switch and its three rotary contact arms are so devised that when one radial portion ,of an arm has traversed its entire strip of segmental contacts, to the segment 2, the diametrically opposite portion of the arm is at segment a. Thus one further step of the contact arm as a whole, beyond a, carries the last-mentioned previously inactive portion onto the starting segment b, conditioning the switch for the next operating cycle.

Referring now to the wiring diagram, Fig. 5, the positive and negative mains from the available electric power source are indicated at 35, 36 respectively.

Assume now that the apparatus is to be used in the performance of an A cycle of operation. For present purposes the desired continuous period of sterilizing heat will be taken as ten minutes. But under the A cycle that tenminute period of maintained heat is determined and controlled directly from the most inaccessible .portion of the load itself, by the thermoswitch 15 there located, or'by the equivalently located insulated thermo-swltch I5. Thus the A cycle timing action does not start until the heat has reached the place which is least accessible to it, whether it take twenty minutes, thirty minutes or even more to reach that point. By contrast,

the B cycle of operation, later to be described,- I functions under a time measurement of continuously sustained sterilizing heat at or adjacent the pleted more quickly than an A cycle.

cool point of the chamber itself, rather'than of the load. The timing period under the B cycle, as herein selected for the purposes of illustration,

is twenty'minutes, and is under the control of the thermo-switch in the chamber discharge passage. From the further description it will be seen that while the measured time period of a "3 cycle herein is twenty minutes and that of an A cycle, now to be described, is but ten minutes, the B cycle frequently may be com- That is due to the difference in the location at which the thermo-control is had, that location being chosen whichis appropriate for the given load tobe sterilized. In other words, during an A cycle there may be a period of thirty minutes or more necessary initially to reach the sterilizing condition and to set the time to running, making a total period of forty minutes or more for the entire cycle; while under thefB cycle effective sterilizing temperature may be reached perhaps .in tenminutes which, plus the twenty-minute measured period, gives a total period of but thirty minutes. v

Assume then that .an fA cycle is to be started, and that the apparatus is cool and the door open. The thermo-switch is positioned at the most heat-resistant place, generally the lower central part of a large bundle, substantially as in Fig. 1. This bundle and any others making up the charge are loaded into the chamber, the thermo-switch being plugged into its socket 19 It will be understood that any number of such thermoswitches may be used if desired, in difierent bundles and in various locations, all of them being wired in parallel. If the insulated thermoswitch 15 is to be used, either in addition to or alternatively for the bundle-positioned thermoswitch 75, it is set into its insulating housing on the door and plugged into the adjacent socket. In the illustrated example'the thermo-switch III at the chamber discharge passage may be used during an A cycle as well as for a B cycle, being in parallel with the others, and for present purposes it is assumed that a therm'o-switch M has been inserted in the chamber discharge passage, as illustrated in Fig. 1, and its appropriate plug-in connections made.

The chamber having been loaded, the door I2 is closed and its radius bolts are projected into bolting position. That operation throws the door-operated switch 48 into the position shown in the diagram, it being again noted that contacts 45 and 48 close first, at an appreciable interval ahead of the closing of contacts 42, 43. At this time or previously the key-operated switch 68 is thrown into its Afcycle position, as shown in Fig. 5, wherein contacts-6| and 62, and 61 and 69 are closed, the others being open.

When cool, as at present assumed, all thermoswitches 10, 15 or 15* have their contacts in closed relation, as shown on Fig. 5. This establishes the thermally-controlled relay circuit, through the thermo-switches, each of which is parallely disposed in circuit with the relay 80. For the thermo-switch I8, this circuit is from the positive main 35, along the wire 46, across contacts 46, 45 of switch 48, through the wires 45 and 13, across closed contacts 1|, I2 of the thermo-switch 10, wire 14, wire 6| and connect ing wire 8| to one terminal -8| of the relay 88, and thence from terminal 82 through the wire 82 out to the negative main 36.

For the thermo-switch 15 or I5 as the case may be, the circuit or circuits through said relay 88 are similar except that they lead through a then closed pair of contacts 6|, 62 of the keyoperated switch 68. Such circuit is from the positive main 35 through wire 46, contacts 46 and 45 of switch 40, through wire 45 to a wire 16 leading to the thermo-switch 15 or J5, or both, across the closed contacts 16, ll of said switch or switches and via wire 11*, to connecting wire 62, through said closed points 62, 6| of the key-operated switch 68, and back on the wire 6| to the connecting wire 8| leading to the terminal 8| of the relay 88. Thus, so long as either or any of said thermo-switches l8, 15 or 15* are cool, that is, below 250 F., and hence have their contacts closed, the relay 8!! is energized and its spring-loaded arms 83 and 83 are held up in contact with the points 84 and 84*.

These closed contacts at 83, 84 and at 83 84 establish what I will term the cool circuits, which are mainly associated with that particular segmental strip or circuit plate of the threeplate rotary switch which is. illustrated at the lower central portion of Fig. 5 and is designated by the numeral IIO. They also involve the solenoid H2 for said rotary switch, then operated through its interrupter device II 1, and the red pilot lamp.

During the cool or pre sterilizing period, immediately following loading and closing of the door, it is desired to lock the door and to light the red pilot, indicating that the temperature at the point or points concerned is below 250 F., and incidentally to condition the hot circuits for operation at the proper time.

The now established door-locking circuit is as follows: from the positive main 35 along the wire 06, across the closed contacts 45, 46 of the dooroperated switch 40 (closed, ahead of the closing of 42, 43, by the shutting and bolting of the door), back along a line 85 to a connection 83 with the arms 83 and 83*, the latter being now in closed engagement with the contacts 8d and 30* respectively. Thence the circuit follows wires 80, 84 and 84 onto the terminal segment a of the circuit plate H0. The circuit established at 83 84 conditions the red pilot lamp, as will be explained.

It will be understood that the respective rotary contact arms III, I2I and I3I of the three circuit plates IIO, I20 and I30, while insulated from each other, are connected each with its own terminal segment a, so as to communicate from such terminal segment a and through the contact arm onto whatever segment the latter then happens to be opposite. It should also be noted that the initial or cool positionof each of the rotary contact arms lII, HI and I3I, all of which always move mmultaneously, is at the respective segments H li0 and I30 Continuing said door-locking circuit, it extends from said terminal segment H0. through the rotary arm III, onto segment II0 and the lead 03' connected with the latter, to contact 53 of the door-operated switch 40. By the closing and bolting of the door said contact 43 became engaged with contact 42, as shown (at an interval after contacts 45, 46 were similarly closed), so that the circuit continues through line 42 and a lead-off wire 42 through connection II'I, interrupter II I and its then closed contacts II8, H3, wires HS! and. H2", and so through the solenoid H2 and out through a wire I I2 to the negative main 35.

This cool" circuit just traced energizes the solenoid II2, through its interrupter, and causes the rotary arm I II to step from segment IIIl to segment IIO, the two other rotary arms I 2i and I3I incidentally taking the same steps. The energized solenoid causes the pawl II5 to wipe over one tooth of the ratchet H6, and actual turning of the ratchet I I6 is efiected' by the reverse movement of the pawl under influence of its spring 5' when the interrupter I I1 breaks the solenoid energizing circuit.

This movement of the rotary arm II i onto segment III) closes the door-locking circuit for the door-locking and switch-operating solenoid 50,

located on the sterilizing apparatus. This second of the cool circuits is the same as previously traced from the positive main 35 to the terminal segment II0' and rotary arm I I I, whence it continues through segment H0 and line 51 51'", to switch point 51. The latter is then in closed engagement with the blade 55 connected by wire 53 with terminal 53 of the locking coil 50 of the solenoid 50. The circuit continues through the solenoid, its common terminal 52 and a wire 52 back onto the negative main 38. Thus the looking plunger 5| is projected into locking engagement with the door. Simultaneously said locking coil 50' throws the toggle switch 55, 58, breaking the circuit at 51 and closing a circuit across the switch blade 56 and a contact 50, for subsequent functioning in connection with the unlocking of tl iie tczioor and with the lighting of the appropriate p 10 Returning now to the main cool circuit established at 83, 84 by the thermally-controlled relay 80, an associated shunt circuit also provides for the lighting of the red pilot 90, by closing the contacts 83 and 84*. The latter is connected by wire 84* through a connecting wire 8, and a wire 90, through the filament of the red pilot 90, and onto'a return lead 36 connecting with the negative main 36.

The established conditions as described now prevail through the remainder of the cool period and until the critical or sterilizing temperature of 250 F. has built up at the locations of each and all of the thermo-switches I0, lb or l5.

At such time, the primary or thermally-controlled relay circuit through the relay 80 is broken, by the opening of the thermo-switch contacts in response to arrival at sterilizing temperature. Said relay being deenergized, the spring-loaded arms 83 and 83 break contact with the points lid and 84*, and close onto the contacts 85 and 35*,establishing or operatively conditioning the so-called hot circuits now to be described.

The rotary switch arms, noting particularly the arms IZI until now have been standing opposite their respective segments c. Heretofore, during the coo period, the circuits at 620 and. 830 have been dead. They now become active, or conditioned for activity, by reason of the described thermally responsive shift of the arms 83 and 03 off of contacts 85 and 84* and onto contacts 05 and 85*. From the positive main 35 to said arms 83 and 03* the circuit remains as previously described, but the shift of said arms onto contacts 85, I35 now serves to connect the terminal segments a of the circuit plates I20 and I30 with the positive side of the line, via wires 05 and 85 and wires 85 and 35, respectively.

One effect of this shift to the hot circuits is to light the green pilot 93 to indicate that sterilizing temperature has arrived and that the measured time is now set to running. This green pilot is controlled through the third circuit plate I30 and its rotary arm MI. The terminal segment I30 of said plate I30 is now in communication with the positive main, via connections 85, 05* and closed contacts 85*, 83 as previously described. The segments b through m of this third circuit plate I30 are connected together. Hence the green pilot circuit continues from segment I30 through rotary arm I3I, onto segment I30 of the connected group of segments I30 to I30 and through wires I32 and I32 to the connection 33 of the filament of the green pilot 93, thence to the pilot return lead 36 and onto the negative main 36. The green pilot accordingly is on.

The shift of the arms 83, 83 to the lower contacts of the diagram, caused by the arrival of sterilizing temperature conditions and accompanying opening of all the thermo-switches 10, I5 or I5 also conditions the time-impulse controlled circuit for measuring oif the sterilizing period. This hot circuit is associated with the circuit plate I 20, whose segment IZII is now in communication with the positive main 35,

through the wires 85 and 85 to contact 85 now engaged by the arm 83.

Since the closing and bolting of the door, the rotary arm I2I of this circuit plate I has stood opposite the segment I2I. The group of ten segments I20 to I20 of this plate are connected together, so that when the arm I2I is opposite any one of them a time measuring circuit, as now to be described, is alert.

This timing circuit is arranged to be periodically closed, say at one minute intervals, under the control of the timing or clock-activated relay I00. This may be in circuit with a master clock IN, or other available source of timed electric or other impulses, as previously mentioned, such as a synchronous motor with appropriately actuated contacts.

'a wire I02 connecting with contact I02 at said time relay I00. When an energizing impulse is received by the latter, it causes the arm IOI to engage said contact I02, thus continuing the circuit through wires I0I I0I and IN to a connection H2, communicating through wire II2 with the solenoid II2, but not going through the interrupter. From the solenoid II2 the circuit is completed onto the negative main 36 via the connector II2 previously noted.

Thus each periodic energizing impulse at the time-controlled relay I00 (or by whatever intermittently acting means is employed to throw the arm IOI at regular timed intervals), energizes the rotary switch solenoid H2 and causes the rotary arm I2I, as well as the others, to move one step. So long as the heat is sustained at the sterilizing temperature this periodic stepping of the rotary arm continues through the block of segments 0 to m of each circuit plate and onto the several segments 12. At the circuit plate I20 the block of segments I20 to I20*, which are connected together, are dead, under an A cycle operation.

At the end of a continuous full timed period of maintained sterilizing heat, all rotary arms I20, I and H0 have reached their respective segments n. The segment I30 of the circuit plate I30 now becomes active. As noted, the rotary arm I3I can thus be brought opposite said segment I30 only when a full continuous measured period of sterilization has been completed, at which time the apparatus is ready for the door to be unlocked and the white pilot 96 to be displayed.

Said rotary arm I3I is connected through the terminal segment I30 with the positive side of the main through the connections 85, 85 and closed contacts 85 03 as previously described. Hence with the arrival of rotary arms I3I at segment I30 the white pilot circuit is now established, from said arm I3I, through segment I30 and a wire 61 to contact 61 of the key-operated switch 60, which is then in closed engagement with contact 69, in accordance withthe setting of said switch for an A cycle operation. From said contact 69 the white pilot circuit continues through a wire 69 to the connector Elli for the filament of the white pilot 06, onto the pilot return lead 36 and so to the negative main 36.

The retraction of the door-locking plunger 5| to unlock the door is simultaneously accomplished through a parallel circuit running from the wire 60 just referred to, through a connection 58 to the toggle switch contact 58. The latter became engaged with switch blade 56 when the door was locked, and the unlocking circuit accordingly continues across said blade 56 and through a connection 54 to the terminal of the unlocking coil 50 of the door-locking solenoid 50. This circuit is completed from the common opposite terminal 52, through wire 52, onto the negative main 36. This energizing of the unlocking coil 50 retracts the locked plunger 5I from the door, permitting it to be opened, and also throws back the toggle switch 55, 55 into its initial position wherein blade 55 and contact 51 are engaged, as shown on the diagram.

The whitepilot informs the attendant that sterilization of the load has been completed and thatthe door is unlocked. He accordingly turns off the steam and opens the chamber exhaust, unless a further shunt circuit through electric valves accomplishes the same automatically. After a brief cooling period the door may be opened and the contents removed, the sterile condition of which is assured.

When the steam is turned off the temperature rapidly drops. The heat-opened contacts of the thermo-switches I0 and I5 or 15 accordingly close and the thermally-controlled circuit through the relay 80, as previously described, is reestablished. The. relay 80 being thus energized shifts the arms 03 and 03 from the contacts 85 and 85 for the hot circuits onto the cold circuit contacts 84 and 84*. In opening the door the contacts 42, 43 of the door-operated switch 40 separate and, somewhat later, contacts 42, 44 close and contacts 45, 40 open, thereby leaving all circuits dead.

In the foregoing description the several rotary contact arms IIO, I 20 and I30 were left opposite their respective segments n. The reestablishment of the "cold circuit at 04 and 84 as just mentioned, places the terminal segment I I0 of the circuit plates H0 in communication with the positive side of the line, as formerly. Ac-

cordingly a resetting circuit is established from.

said segment II0 through the rotary arm III and segment II0 (segments II0 through 0 being connected in a block), through a wire 42,

to the conductor 42*, thence through the interrupter III and rotary switch solenoid H2, and back onto the negative main 36, thence through the interrupter Ill and rotary switch solenoid H2, and back onto the negative main 36. Hence the resetting circuit as just traced, through the segment H0, energizes the solenoid H2 and causes the several rotary arms to step around from their position n successively over the following segments, through segment 11, and onto segment 2. This travel of the rotary arms over the entire left quadrant of their segment platesis accomplished through the successive but intermittent operation of the solenoid by the interrupter I I I.

On arrival of the contact arms at position 2, and referring now particularly to the contact arm III of the circuit plate IIO, a final circuit is there established, from the terminal segment H0 through the arm III and segment 0 through a wire 44 connected with the latter, to contact 44 of the door-operated switch 40. The latter is now in engagement with contact 42, -by reasonof the opening of the door. Hence the circuit is continued from said contact 42 through the wires 42 and .42, onto the interrupter connection II 1, and through the interrupter and solenoid H2, back onto the negative main 36.

The solenoid H2 is thus given a final energization, which steps the three rotary arms IIO. I20 and I30 one further step beyond their respective segments .2. .This brings the diametri cally opposite portions of said arms onto the respective starting segments Iiil, and 30, so that the whole system is restored to original condition, in readiness for the next sterilizing operation.

In the preceding description it has been assumed that the sterilizing temperature condition's, once established, have continued to prevail through the full period intended, without interruption. Assume now that at some time after the sterilizing period has begun to be measured off, a failure of heat occurs, for any reason whatsoever, whether due to failure of the steam supply, or through tampering with the steam valves by the attendant by an attempt to cut short the sterilizing period, or for any other reason. The ensuing temperature drop at any of the critical points represented by the therrno-switches I0, 15 or I5 causes one or more of said devices to make contact and so to energize the thermocontrolled relay 80, shifting the arms 83, 83 and throwing the system from the hot circuit condition back to the cool circuit condition.

The resulting effect is precisely the same as previously described in connection with a normal reestablishment of the cold circuit attendant on turning off of the steam on completion of a full stearilizing period, with the exception of course that the white pilot is never displayed and the door is not unbolted, because the rotary arms have not reached their segments 12.. This return of the cold circuit condition now referred to, as caused by'heat failure during a sterilizing period, reestablishes the previously described interrupter circuit at the plate H0 and causes all the rotary arms to step around in rapid succession over all of the segments to the segments .2.

Since the door remains closed and bolted some arrangement is necessary to carry the rotary arms from this 2 position one step further so that their opposite portions reach the initial or b position and then step to 0 position, where they will be ready, having reference particularly to the rotary arm I2I, to resume the time measurement when the sterilizing temperature returns and the hot circuit is again established. To accomplish this the final segment 2 of plate I20 is connected by a wire I22 with the wire I22 leading thro Wire II'I to the interrupter. This circuit serves to effect one of the steps referred to, bringing the appropriate ends of the rotary arms opposite their segments b. At the circuit plate I20 the single segment b is unconnected with the others and now serves to effect one further step of the rotary arms, from the segments b to c. This is herein accomplished by connecting said segment I20 through a wire I22 with the wire I22 and thence through the interrupter H1.

These emergency circuits, at segments I20 and I20", which function only with a heat failure, thus bring the rotary arms back onto segments 0, in readiness to start again upon another time measurement, when the proper temperature conditions again prevail. It is particularly to be noted that the time measurement is thus caused to be repeated in full. It does not simply resume at the point where it left off, but the entire timing cycle is caused to be repeated. Thus only a continuous period of maintained predetermined temperature conditions at the selected critical points can be effective to release the chamber closure or door, as contrasted with a mere total or cumulative period made up of interrupted sulated point within the sterilizer receptacle (thermo-switch 15) Under a 3" cycle or method of operation the apparatus as herein illustrated is arranged to operate also through a continuous period of maintained heat, which may be determined exteriorly of the load, as, for example, by the use of the thermo-switch 10 alone. This latter, as previously noted, is installed at what may reasonably be taken as the coolest point of the sterilizer system or receptacle, namely, in the path of the steam and condensate discharge. For packages, articles, utensils or the like which are not particularly difficult to sterilize, a temperature reading or indication at such point, if maintained for an adequate period, including an ample safety factor, may be considered suflicient. For the present purposes it is assumed that such period, for a 3" cycle operation, is twenty minutes.

To operate the apparatus under a B cycle, the key-controlled switch 60 is thrown, by the authorized responsible person to whom the key is entrusted, to the B position, as represented by the arrow and the letter B in association with said switch 60 on the diagram. This throws the movable elements of said switch to the left, on the diagram. closing the contacts 68 and 69, 65 and 66, and 63 and 64.

The operation under such B cycle is essentially the same as already described in detail for an A cycle, but using only the thermo-switch I0, with the main exception that the time period as measured off, after a sterilizing temperature at the control point has been attained, is longer, in this instance, twice as long. After the rotary arm I2I has progressed through the first block of segments it comes opposite the segment n, as under an A cycle. But under a "3 cycle the second block of segments n to a at the circuit plate I20 is active. Said segments I20 to I20 are connected together and are connected through a wire M and through the closed contacts, 63 and lead 63 with the connection I02 leading to the contact I02 which is to be closed by the timed-impulse-actuated relay I00. Thus the block of segments I10 to I20 is rendered actively subject or alert to such timed impulses in the same manner as were the segments I20 to Under the B cycle the green pilot 93 remains lighted, to indicate the continuing presence of a sterilizing temperature, throughout the longer period, by means of a connection 9t with the block of segments I30 to I30 and communieating with the lead 93 for the green pilot. Likewise the white pilot, for indicating completion of the full continuous period and unlocking of the door, does not show until completion of the full continuous longer period. This is accomplished by means of the separate segment I30 which is not reached by the rotary arm I3I until the end of the "B" timing period. Said segment 1! is connected through a wire 58 with the contact 68, now in closed engagement with the contact 69 and thence through the wire 69 and connector 96 to the filament of the white pilot.

Failure of heat, for any reason, and at any time prior to completion of the full B cycle sterilizing period, causes the whole cycle to repeat and begin anew the timed measurement of the predetermined maintained temperature, similarly as in connection with the A cycle of operation as already described.

It will be understood that the A and "13 operating cycles as herein illustrated are merely representative of two possible arrangements and that they may be modified or supplemented, as by provision of additional contacts at the key-controlled switch 60 and by the provision of additional segments or extra circuit plates and associated rotary switch arms. As previously stated, my invention contemplates that the load or contents of a sterilizing receptacle shall be positively restrained against removal prior to the expiration of a continuous predetermined period of maintained effective sterilizing temperature conditions at a selected minimum temperature. Various modifications within the broad spirit of the invention will occur to those skilled in the art. As above indicated, automatic electric valves for the steam supply and steam exhaust may be tied in with the system as described, as by means of parallel circuits connected similarly as for the white pilot. Iii-desired, visual recording means also may be associated with the appropriate circuits.

Referring now to Figs. 8, 9 and 10, means embodying my invention, and for practising the method thereof, is there illustrated in connection with a heat-treating apparatus or sterilizer of the liquid or liquid and steam type, as commonly used for sterilizing instruments, utensils and such.

The apparatus as there shown by way of example comprises a supporting frame I for a receptacle, tank or chamber I8I provided with a closure member I02, illustrated as a hinged cover. The apparatus includes the usual supply and outlet pipes for water and steam. For example, a water supply-pipe and valve are indicated at I43, having a safety connection to a drain bucket I84, the latter adapted to be connected to the drain. A steam pipe and valve are indicated at I 45 and a drain connection and valve at I48. The usual discharge outlet .for steam, or steam mixed with air and condensate, is shown at I 41, being connected through a pipe I48 to a drain bucket I8 3 which may communicate with a drain. A vent to atmosphere is indicated at I49 and a protective inlet or water filling device at I50. r

In this type of apparatus the cover or lid for the tank is arranged for convenient opening and closing by the attendant oroperator, generally through pedal-operated means, such as shown in Figs. 8 and 9 by way of example. Such means includes lift rods I5I pivotally connected with the cover I412. The lower ends of the lift rods I5I are pivoted to arms I52 fixed on a rock shaft I53 suitably mounted on the apparatus, as upon the supporting frame. Said lift rods and rock shaft are arranged for foot operation, by a 'pedal I58 on a two-arm lever pivotally mounted on the frame as at I55 and pivotally connected to a link I56 in turn pivoted to an arm I51 fixed on the rock shaft I53.

As illustrated by way of example in Fig. 9, the

tank I8! preferably, is equipped with a tray or basket I58 for the instruments or utensils to be sterilized, the basket being operatively associated with the cover I42 so that it is automatically lifted or depressed with the opening or closing of the latter. This may be accomplished as through the links H9, at opposite ends of the basket, pivotally connected with the cover and with the basket. The connection with the basket may include cooperating segment arms I00 mounted on lift brackets IBI. By some such means the basket is disposed for lifting and depression, in level condition, with the opening or closing, respectively, of the cover.

Heretofore, so far as I am aware, the control of a heat-treating or sterilizing apparatus such as that of Figs. 8 and 9 has been left entirely to the will of the attendant, who places the instruments, utensils or other articles in the tank or in the basket therein, closes the cover, admits the water or water and steam and at the end of a supposedly adequate interval, on which there is no check whatsoever, opens the tank and removes the presumably sterilized articles. In accordance with my invention the receptacle or tank, once loaded and closed, is automatically locked against opening and against removal of the load, pending the expiry of a predetermined consecutive period of maintained heat at a selected minimum temperature, similarly as in connection with the apparatnus of Figs. 1 to 7. The controlling means may be substantially similar to that previously illustrated and described in connection with said Figs. 1 to 7.

As seen in Fig. 8 and upon a larger scale in Fig. 10, the locking element proper may comprise a combinedsolenoid and toggle device I18 which may correspond in all respects with the element 58 of the previous figures. The locking plunger HI of said device is arranged to enter a locking formation or recess I12 in the rock shaft I53, which is brought opposite the plunger when the cover is closed.

A multiple contact switch I80 is provided, corresponding in construction and arrangement with the door-and-bolt operated switch device 50 of the previous figures. The double contact member I82 and the other contacts I88, I88, I85, I86, are arranged for similar operation as the corresponding members of said switch 40, including the provision for closing of contacts I85, I86 at an appreciable interval in advance of closing of contacts I82, I83, in connection with the closing and locking of the cover, and for similar advanced opening of the contacts I82, I83, with respect to the opening of contacts I85, I86 and the closing of contacts I82, I84, in association with the unlocking and opening of the closure or cover I42.

In. this instance the switch I80 is arranged for operation through an extension I 87 of the double contact arm I82 which is engageable by the cam shaped head I88 of a spring-pressed plunger I89. The latter is moved out of contact with said extension I81, by its spring,,when the lid or cover I42 is open, and is depressed into' the position illustrated in Fig. 10, attendant on closing of the cover, to operate the switch I80, through the medium of aneccentric or cam I90 fixed on the rock shaft I53. Thus, in the apparatus of Figs. 8 to 10, the turning of the rock shaft I53 attendant on closing of the cover accomplishes for the switch I80 the same function as is accomplished for the switch 80 of Figs. 1

to 17 during the closing and bolting oi the chamber door l2.

The described electrically operated look no and the closure-controlled switch I may be mounted on or in association with the apparatus of Figs. 8 and 9 in any convenient manner. In the illustrative instance one of the hollow uprights of the frame is provided with an enlargement or housing portion I9! within which is a removable bracket or shelf I92 on which said lock and switch are hung or otherwise supported.

The electrical connections and circuits, including the relays, key-controlled switch, rotary switch, pilots and other parts, may be the same as already fully illustrated and described in connection with the previous figures, having reference particularly to Figs. 4, 5, 6 and 7. In the apparatus of Figs. 8 to 10 a thermo-switch 995, corresponding to the thermo-switch 10 of the previous figures, is installed at a cool point in or in association with the tank or receiver Mi. As shown in Figs. 8 and 9 said thermo-switch is set in operative position across the discharge outlet Ml for the steam, air and condensate or mixtures thereof, where it is adapted to function in a similar manner as said thermo-switch 10 of Fig. 1.

It will be understood that one or more similar switches may be employed similarly as in the preceding figures, at any other preferred or characteristiclocation in or in connection with the illustrated apparatus, and such provision may include that of a predeterminedly heat-insulated thermo-switch corresponding to the element E5 of Figs. 1 to 5. As in the previous instance, failure of heat at any time after the institution of a sterilizing cycle preferably will cause the entire cycle to be repeated, thereby insuring that the instruments, utensils or other articles comprising the load may not be removed unless and until they have been subject to the desired degree of tmperature, either in the hot or boiling bath, or in the atmospheric or other steam, throughout a consecutive timed interval. Nothing which the attendant or operator can do,

either deliberately or otherwise, unless he has access to the key for the key-controlled switch tit, can prevent said desired result. It will be understood that suitable provision may be made for emergency release of the lock, such as a key: controlled means for throwing the locking: plunger iii to releasing position, such key, simi= larly as that for the switch tn, being available only to some authorized responsible person.

It will be understood that my invention, either as to means or as to method, is not limited to the exemplary embodiments or steps herein illustrated and/ or described, its scope being set forth in the following claims.

I claim:

1. In a sterilizing apparatus, in combination, a sterilizing receptacle, locking means to pre vent removal from the receptacle of the contents to be sterilized, releasing means for the locking means, timing means to determine the operating time for said releasing means, and means thermally responsive to a predetermined receptacle temperature for operatively conditioning the timing means, the construction and arrange-= ment being such that any interruption of the timing means by the thermally responsive means during an instituted timing cycle causes the cycle to be repeated in full when resumed.

2. In a sterilizing apparatus, in combination, a sterilizing receptacle, locking means to prevent removal from the receptacle oi the contents to be sterilized, and thermally conditioned timing' means to release the locking means when the sterilizer contents have been subject to a predetermined temperature measured at a point such as to signify adequate heat penetration of the load and maintained for a selected consecutive time period.

3. In an apparatus for sterilizing purposes, the combination of a receptacle for contents to be treated; means supplying the heating medium; locking means for retaining the receptacle contents subject to the heating medium; a timing device controlling said locking means; and mechanism responsive to a predetermined temperature with respect to the receptacle and contents, for starting, interrupting, and restarting the timing device in full repeat, in accordance with the arrival, continuance, failure, and recurrence of said temperature.

a. In a sterilizingapparatus in combination, a chamber adapted to receive a load to be sterilized, means for admitting a heating fluid to the chamber, a closure member for the chamber, bolting means for the closure member, a thermally responsive element operatively positioned so as to be affected by heat in the chamber, and means controlled by said element to release said bolting means only after a period of predetermined continuously sustained minimum temperature effective on the load in the chamber.

5. In a sterilizing apparatus, in combination, a chamber adapted to receive a load to be sterilized, means for admitting a heating fluid to the chamber, a closure member for the chamber, bolting means for the closure member, a thermally responsive element operatively positioned so as to be adected by heat in the chamber, means controlled by said element to release said bolting means only after a period of predetermined continuously sustained minimum temperature eiiective on the load in the chamber, and signal means associated with said thermally responsive element and with said switch means to indicate a cool status of said element, a predeterminedly heated status, and the expiry of said predetermined sustained minimum temperature period requisite to the releme of said bolting means.

6. in combination, in a sterilizing apparatus, a sterilizing receptaclefa charging door for the receptacle, locking means for the door, and means preventing unauthorized unlocking and opening of the door, subsequent to loading of the receptacle and starting the sterilizing operation, until a selected minimiun temperature condition has been continuously maintained in the receptacle for a predetermined period adaptable to the character of the load being sterilized.

7. In a heat-treating apparatus, in combination, a receptacle for a load to be treated, locking means to prevent removal of said load from the receptacle, and jointly heat and time controlled means for releasing said locking means only upon expiry of a predetermined consecutive period of a maintained selected temperature effective throughout the receptacle load.

8. In a heat-training apparatus, in combina tion, a receptacle for a load to be treated, locking means to prevent removal of said load from the receptacle, means to release said locking means after a predetermined measured consecutive time period, and means responsive to a selected temperature at a relatively cool location with respect to the receptacle and its load for 75 rendering operative the timing means associated with said releasing means.

9. In a sterilizing apparatus, in combination, a sterilizing receptacle, locking means to prevent removal from the receptacle of the contentsto be sterilized, releasing means for the locking means, timing means to determine the operating time for said releasing means, and thermally responsive means for operatively conditioning the timing means upon predetermined heat exposure of the load, the construction and arrangement being such that any interruption of the timing means by the thermally responsive means during an instituted timing cycle causes the cycle to be repeated in full when resumed.

10. sterilizing apparatus comprising, in combination, a receptacle for a load to be sterilized, movable means for retaining the load in the receptacle, locking means associated with said movable means to prevent untimely removal of the load from thereceptacle, and jointly heat and time controlled means operatively associated with the receptacle for releasing said locking means only upon expiry of a predetermined consecutive time period of continuance of a predetermined minimum temperature efiective upon the load.

11. sterilizing apparatus comprising, in combination, a receptacle for a load to be sterilized, movable means for retaining the load in the receptacle, locking means associated with said movable means to prevent untimely removal of the load from the receptacle, time-controlled releasing means for said locking means arranged to be operative after a predetermined measured consecutive time period, and temperature-responsive means for rendering said time-controlled means operative, said temperature-responsive means being so constructed, arranged and located with respect to the receptacle and its load that a predetermined temperature effective on said temperature-responsive means to cause actuation thereof can occur only after a time period sufiicient for heat in the receptacle adequately to have penetrated the load therein.

12. In a sterilizing apparatus, in combination, a receptacle within which sterilizing heat is to be applied to a load, a closure for the receptacle, locking means associated with the closure to prevent untimely removal of the load under treatment, and time-and-temperature-responsive means so controlling the locking means as to allow opening'of the closure and removal of the treated load only after a prescribed continuous period of a maintained minimum temperature.

13. In a sterilizing apparatus, the combination with a receptacle for the load anda receptacle closure, of locking means for the closure conditioning the receptacle against opening of the closure, and automatic mechanism for releasing the locking means, said mechanism being responsive to a selected temperature maintained for a predetermined consecutive period.

14. In a sterilizing apparatus for medical and surgical purposes, in combination, a receiver for the load, a door for the receiver movable to open and to close the same, means positively to lock the door in closed position, operating means for the locking means, and automatic thermal and temporal control means conjointly operatively associated directly with said lock-operating means to effect a releasing action thereof only after a prescribed continuous heated time.

15. In a sterilizing apparatus formedical and surgical purposes, in combination, a receiver for the load, a door for the receiver movable to open and to close the same, means positively to lock the door in closed position, electro magnetic means for controlling said door-locking means, and control mechanism for said electro-magnetic means normally operative to cause the latter to release the lock means only on expiry of a predetermined continuous period of minimum temperature in the receiver.

6. In a sterilizing apparatus for medical and surgical purposes, in combination, a receiver for the load, a door for the receiver movable to open and to close the same, means positively to lock the door in closed position, and automatic temperature-controlled timing means for said doorlocking means toprevent release of the latter prior to the end of a minimum continuous period of the prescribed temperature in the receiver.

17. In a sterilizing apparatus'for medical and surgical purposes, in combination, a receiver for a load. to be sterilized, a movable closure for the receiver, locking "means for positively retaining the closure in closed position against unauthor ized opening, releasing mechanism for said looking means, time-measuring means directly operatively connected to cause operation of said releasing mechanism, and means thermally retration prior to operation of the releasing mech-' anism.

l8. sterilizing apparatus in accordance with claim 1'7 including means for selecting as between a plurality of different operating periods for said time-measuring means.

19. sterilizing apparatus in accordance with claim 17 including means for selecting as between a plurality of different operating periods for said time-measuring means and means for locking said selecting means against operation by an unauthorized person.

20. sterilizing apparatus in accordance with claim 17 wherein the thermally responsive means includes a thermostatic element carried at the inner face of the receiver closure.

21. In a sterilizing apparatusfor medical and surgical purposes, in combination, a receiver for a load to be sterilized, means for supplying heat to the receiver and its load, closure means for the receiver, locking mechanism for the closure means, and control means for the locking mechanism normally compelling retention of the load by the receiver pending the expiry of a predetermined consecutive period of a maintained minimum temperature efiective on the load in the receiver.

22. In a sterilizing apparatus, in combination, a receiver for loads to be sterilized, means for subjecting loads in the receiver to heat, electrical means associated with the receiver -for actuation when heat therein at a predetermined temperature has penetrated the load, an operating circuit for said means, a self-contained thermo-switch in said circuit, said switch comprising a bodily removable unit and associated flexible electrical conductor means, and a socket in the receiver for readily removably positioning the switch, said socket having heat-penetration resisting properties equivalent to those of the load.

23. In a sterilizing apparatus, in combination a chamber adapted to receive a load to be sterilized, means for admitting a heating fluid to the chamber, a timing mechanism, a thermally responsive element subject to temperature conditions in the chamber and having a cool status or a heated status depending on the absence or presence of a predetermined minimum temperature conditon in said chamber, electric switch means controlled jointly by said element and by said timing mechanism for actuation only after a selected minimum continuous period of maintained minimum temperature, and electric signal means associated with said thermally responsive element and with said switch means to indicate the condition corresponding to the cool status of said element, the condition corresponding to its heated status, and the expiry oisaid selected minimum continuous period of said heated condition.

24. In an organized apparatus an operating cycle of which comprises the attainment of a given operating condition and the maintenance thereof for a minimum continuous period, timing means for measuring the selected minimum continuous period, electrically operated means to start a time-measuring operation of the timing means on arrival of said given operating condition, and associated electrically operated automatic means to interrupt and to re-set said timing means upon failure of said operating condition short of the minimum continuous period selected.

25. In a sterilizing apparatus, in combination, a sterilizing receptacle, a closure therefor, a locking device for the closure, electrically operated releasing means for the locking device, a thermal switch device so constructed and located as to be responsive solely in the event of and during adequate sterilizing heat penetration of the receptacle contents, timing means controlled by the temperature responsive action of said thermal switch device, and means whereby the timing means so controls the releasing means for the locking device as to lock the contents inthe receptacle pending continuous sterilizing heat penetration thereof for a timed period.

26. In a sterilizing apparatus, in combination, a receiver for a load to be sterilized, a heat source for said receiver, means to control application of heat to the receiver from said source, thermal switch means constructed and positioned to be respcnsive only in the event of and during a temperature thereat significant of adequate heat penetration of the load, timing means controlled by said thermal switch means, and locking means for the receiver in turn so electrically controlled by said timing means as to confine the load in the receiver against unauthorized removal pre= maturely as to a minimum time of maintained heat at the prescribed temperature.

27. In a sterilizing apparatus, in combination,

I a receiver for a load to be sterilized, a heat source for said receiver, means to control ap- 1 plication of heat to the receiver from said source,

locking means effective in its locked condition to confine a load in the receiver, a timing device electrically connected with the locking means to efiect the release thereof, and thermal means responsive only to a temperature condition in the receiver significant of adequate heat penetration of the load, for starting said timing device in the presence of such temperature condition and for stopping it in the absence thereof. I

28. In a sterilizing apparatus, in combination, a receptacle for a load to be sterilized, means to supply heat to the load in the receptacle, a closure for the receptacle, a locking device-for the closure the locking of which normally prevents removal of the load prior to an automatic release of said device, and automatic releasing mechanism for the locking device including both time and temperature controlled means conjointly electrically associated with said locking device to release the latter only in the event of complete subjection of the load to heat at a temperature and for a continuous period adequate for sterilization.

29. In a sterilizing apparatus, in combination, a receptacle for a load to be sterilized, means to supply heat to the load in the receptacle, 2. closure for the receptacle, a locking device for the closure the locking of which normally prevents removal of the load prior to an automatic release of said device, and automatic releasing mechanism for the locking device including both time and temperature controlled means conjointly electrically associated with said locking device to release the latter only in response to actual heat-subjection of the load at a temperature and for a continuous time adequate to destroy bacterial life therein.

3 In combination, in a heat-treating apparatus having a receiver for loads to be treated,

mechanism and again to receive an inoperative status prior to re-opening of the latter and to retain said inoperative status while the closure mechanism is open, an operating circuit for said element, a preliminary circuit for conditioning said operating circuit, and a plurality of pairs of electric contacts associated with the closure mechanism for actuation on closing movement thereof, one pair in said preliminary circuit and another in said operating circuit, said first pair constructed and arranged to be closed ahead of the second pair, thereby to establish the preliminary circuit so as to condition the operating circuit for establishment by closing of said sec= and pair.

31. Heat-treating apparatus according to claim 30, wherein said contacts function in the reverse timed order in conjunction with an opening movement of the closure mechanism.

32. In a sterilizing apparatus, in combination, a receiver, a closure therefor, locking means for the closure, a thermoswitch at the free end of a freely manipulable flexible electrical cable connection therefor adapting it to be placed in a region of minimum heat accessible in the load in the receiver, said thermoswitch constructed to be set for a sterilizing temperature, timing mechanism operatively controlled by said thermoswitch, and connections between the timing mechanism and the closure locking means to release the latter.

33. Control mechanism for the closure of a sterilizer comprising, in combination, a movable locking element cooperable with the closure, means to move said element to lock the closure for a sterilizing operation, electrically actuated time-measuring mechanism, operating connections between the latter and the element moving means to efiect releasing actuation of said moving means, a thermoswitch to be so placed in the sterilizer and with such temperature setting that said thermoswitch is responsive to a temperature condition in the sterilizer which is significant oi sterilizing heat penetration of the sterilizer load, and. connections between the thermoswitch and the time-measuring mechanism to start and to stop the latter in accordance with the status oi the thermoswitch.

34.. In a control mechanism for sterilizing apparatus, in combination, a thermoswitch adapted to be predeterminedly set for sterilizing temperature of the sterilizer load, a relay in circuit with the thermoswitch, a closure locking device and electrical operating means therefor in a circuit controlled by the relay, a closure-operated switch also in said last-named circuit, whereby when the closure is closed and sub-sterilizing temperature is present as determined by the thermoswitch the closure is locked by said device, time-measuring means operatively conditioned to becomeactive upon arrival of sterilizing temperature as detected by the thermoswitch, and connections between the time-measuring means and the closure locking device to release the latter at the end of a predetermined time interval following actuation of said time-measuring means.

35. Sterilizer control mechanism as in claim 34 wherein the time-measuring means is constructed and arranged to halt and to re-cycle on recurrence of sub-sterilizing temperature prior to expiry of a minimum uninterrupted interval of sterilizing temperature as detected by the thermoswitch.

36. Control mechanism for a sterilizer having a load receptacle and a closure device including operating means therefor, said mechanism comprising, in combination, an electrically operated lock for the sterilizer closure device, switch means and connections for said lock adapted for association with the closure device in such manner that a closing operation of the latter automatically effects a locking action of said closure lock, a thermoswitch responsive to the presence or absence of a predetermined degree of heat in the receptacle, a time-controlled accumulating relay in circuit with the thermoswitch for operative control thereby, and connections between said relay and the closure lock to release the latter only after a predetermined accumulative actuation of the relay. 1

, 37. Control mechanism for a sterilizer having ing a closure, said mechanism comprising, in combination, a thermoswitch having positions respectively to be determined by the presence or absence of a predetermined degree of heat of the sterilizer, a relay controlled by the thermoswitch,

one or more cool" circuits establishable through the relay, in the non-heated position of the thermoswitch, one or more "hot circuits operatively conditionable through the relay in the heated position of the thermoswitch, a closure lock and electro-magnetic means to control its locked and being connected to effect unlocking of the latter only on arrival of said contact element of the time-controlled switch at its objective position.

38. Sterilizer control mechanism according to claim 37 including means to restore the mechanism as a whole automatically to its initial position on completion on an operating cycle.

39. Sterilizer control mechanism according to claim 37 wherein the time-controlled switch contact element is caused to return to initial position in the event of return of the thermoswitch to non-heated position prior to an arrival of said element at its objective position and thereafter to re-cycle on restoration of the thermoswitch to its heated position.

40. In a control mechanism for sterilizing apparatus having a load-chamber and a closure therefor, in combination, a thermoswitch adapted to be predeterminedly set for sterilizing temperature of the sterilizer load, a circuit-establishing switch in the thermoswitch circuit arranged for closing attendant on a closing operation of the closure, said thermoswitch circuit also including a relay, time-measuring means associated with the relay to be rendered active by it on arrival of sterilizing temperature as detected by said thermoswitch, closure-locking mechanism for locking upon closing operation of said closure, releasing means for said closure-locking mechanism, and connections between the timemeasurlng means and said releasing means to cause the latter to release the closure-locking mechanism at the end of a predetermined time interval following actuation of the time-measuring means.

41. Control mechanism for a sterilizer having a load receptacle and a closure device including operating means therefor, said mechanism comprising, in combination, means for automatically locking the closure device upon closing operation thereof, a thermoswitch responsive to the presence or absence of a predetermined minimum temperature in the receptacle, a time controlled accumulating relay in circuit with the thermoswitch for operative control thereby, and connections between said relay and the closure lock to release the latter only after a predetermined minimum accumulative actuation of the relay.

42. A sterile-locking control for fluid-heated sterilizing apparatus wherein the load chamber has a closed operating condition and has a door for so operatively closing it, said control comprising a locking element to establish a locked status for the door upon operative closure of the latter and subsequently to release the door from said status, actuating means for said releasing operation of the locking element, a thermally actuated device responsive to a predetermined minimum temperature efiective on the locked load, a time-measuring device responsive to the action of said thermally actuated device, and operating connections between said time-measuring device and the release-actuating means for the lockingelement, the thermally actuated device and the time-measuring device conjointly controlling and maintaining the closing-initiated locked status of the door so as positively to impound the load for a predetermined minimum time period at a predetermined minimum temperature efiective on the locked load.

- CARL W. WALTER.

&

CERTIFICATE OF CORRECTION. Patent No. 2,208,552. July 16, 191m.

CARL w. WALTER.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 11, second column, line 68, claim8, for "heat-training" read --heat-treating--;

page 15, second column, lin 58, claim52, for the word "accessible" read -accessibility--; page 114., second column, line 7, claim 58, for "on an" read "of an-; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 5rd day of September, A. D. 191w.

Henry Van Arsdale, (Seal) I Acting Commissioner of Patents.

CERTIFICATE OF CORRECTION. Patent No. 2,208,5 2. Jul 16, 191m.

CARL W. WALTER.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 11, sec- 0nd column, line 68, claim8, for "heat-training" read --heattreating-; page 15, second column, line 58, claim 52, for the word "accessible" read --accessibility--; page 114., second column, line 7, claim 38, for "on an" read -oi an--- and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office. 7

Signed and sealed this 5rd day of September, A. D. 1914.0.

. Henry Van Arsdale, (Seal) Acting Commissioner of Patents. 

